Manufacturing Method for Electrode Assembly

ABSTRACT

An electrode assembly manufacturing method includes the steps of: assembling an electrode stack; performing a primary heat press operation on the electrode stack; then performing a pre-heating operation on the electrode stack; and then performing a secondary heat press operation on the electrode stack. The pre-heating operation may include applying heat and pressure to the electrode stack for a time period from 10 seconds to 40 seconds under a pressure condition from 0.5 MPa to 2 MPa and under a temperature condition from 50° C. to 85° C. The pressure condition applied in the pre-heating operation may include applying a lower pressure than that applied in the primary and secondary heat press operations. The primary heat press operation may include engaging the electrode stack with a gripper to secure a position of the electrode stack, which gripper may be disengaged from the electrode stack before performing the pre-heating operation.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority from Korean Patent Application No.10-2021-0090600 filed on Jul. 9, 2021, Korean Patent Application No.10-2021-0090588 filed on Jul. 9, 2021, Korean Patent Application No.10-2021-0090589 filed on Jul. 9, 2021, Korean Patent Application No.10-2021-0090590 filed on Jul. 9, 2021, Korean Patent Application No.10-2021-0090591 filed on Jul. 9, 2021, Korean Patent Application No.10-2021-0090592 filed on Jul. 9, 2021, Korean Patent Application No.10-2021-0090596 filed on Jul. 9, 2021, Korean Patent Application No.10-2021-0090597 filed on Jul. 9, 2021, Korean Patent Application No.10-2021-0090598 filed on Jul. 9, 2021, and Korean Patent Application No.10-2021-0090601 filed on Jul. 9, 2021, the entire contents of all ofwhich are incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to an electrode assembly manufacturingmethod.

BACKGROUND ART

Secondary batteries, unlike primary batteries, are rechargeable, andhave been widely researched and developed in recent years due to theirsmall size and large capacity. As technology development and demand formobile devices increase, the demand for secondary batteries as an energysource is rapidly increasing.

Secondary batteries can be classified into a coin-type battery, acylindrical battery, a prismatic battery, and a pouch-type battery,according to the shape of the battery case. In a secondary battery, anelectrode assembly mounted inside a battery case is achargeable/dischargeable power generating element having a stackedstructure comprising electrodes and separators.

The electrode assembly may be generally classified into a jelly-rolltype, a stack type, and a stack-and-folding type. In the jelly-rolltype, a separator is interposed between a sheet type positive electrodeand a sheet type negative electrode, each of which are coated with anactive material, and the entire arrangement is wound. In the stack type,a plurality of positive and negative electrodes are sequentially stackedwith a separator interposed therebetween. In a stack-and-folding type,stacked unit cells are wound with a long-length separation film.

In a stack-and-folding type electrode assembly, there has been a problemin that the position of the electrode is distorted from the form inwhich the separator is folded in a zigzag manner and the electrodes arepositioned therebetween.

SUMMARY OF THE INVENTION

The present invention provides, among other things, an electrodeassembly manufacturing method that prevents cell damage and deformationof mechanical parts in the process of manufacturing the electrodeassembly, involving the stacking of electrodes with a separator.

The present invention also provides an electrode assembly manufacturingmethod capable of preventing electrodes from being distorted during themanufacturing process.

An exemplary aspect of the present invention provides a method ofmanufacturing an electrode assembly. The method in accordance with suchaspect of the invention preferably includes the steps of: assembling anelectrode stack; then performing a primary heat press operation on theelectrode stack; then performing a pre-heating operation on theelectrode stack; and then performing a secondary heat press operation onthe electrode stack. The electrode stack assembled in the assemblingstep preferably includes a plurality of electrodes stacked along astacking axis with a respective separator portion positioned betweeneach of the electrodes. In each of the primary and secondary heat pressoperations, heat and pressure may be applied to the electrode stack. Thepre-heating operation may include applying heat and pressure to theelectrode stack for a time period from 10 seconds to 40 seconds under apressure condition from 0.5 MPa to 2 MPa and under a temperaturecondition from 50° C. to 85° C. Moreover, the pressure condition appliedin the pre-heating operation may include applying a lower pressure thanthat applied in the primary and secondary heat press operations.

In accordance with some aspects of the invention, the primary heat pressoperation may include engaging the electrode stack with a gripper tosecure a position of the electrode stack, where the application of heatand pressure to the electrode stack during the primary heat pressoperation occurs while the gripper is engaged with the electrode stack.

In accordance with some other aspects of the invention, the method mayinclude disengaging the gripper from the electrode stack beforeperforming the pre-heating operation.

In accordance with some aspects of the invention, the separator portionsmay be portions of an elongated separator sheet. In such aspects of theinvention, the step of assembling the electrode stack may includealternately stacking a first one of the electrodes and a second one ofthe electrodes on the elongated separator sheet. Moreover, the elongatedseparator sheet may be sequentially folded over a previously-stacked oneof the first and second electrodes before a subsequent one of the firstand second electrode is stacked.

According to the present invention, by heating and pressing the entirestack with the press unit, the electrodes may be bonded to the separatorwithout the need to individually heat and/or press each level of theelectrode assembly (i.e., heating and/or pressing each electrode andseparator pair at each step of the process). heating and stacking theelectrode and the separator. As a result, it is beneficially possible toavoid the detrimental accumulation of heat and/or pressure in the lowerseparators in the stack, and thereby reduce the likelihood of damage anddeformation of the components of the electrode assembly.

According to the present invention, the heating and pressing the stackdesirably occur under low temperature and low pressure conditions duringat least some of the steps of the process. Thus, the inventive methodmay beneficially reduce deviations in: adhesive force between theelectrodes and the separator, air permeability of the separator, andthickness of the manufactured electrode assembly, thereby resulting inincreased uniformity.

By pressing the entire stacked stack with the press unit, the inventionalso desirably reduces any distortion or shifting of the positions ofthe electrodes in the electrode stack. Beneficially, that may result inreduced manufacturing time, as well as improved energy density of themanufactured electrode assembly.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram schematically illustrating a method of manufacturingan electrode assembly according to an exemplary embodiment of thepresent invention.

FIG. 2 is a top plan view illustrating an example of an electrodeassembly manufacturing apparatus according to an exemplary embodiment ofthe present invention.

FIG. 3 is a front elevation view conceptually illustrating the electrodeassembly manufacturing apparatus according to the exemplary embodimentof the present invention.

FIG. 4 is a cross-sectional view illustrating an electrode assemblymanufactured by the electrode assembly manufacturing apparatus accordingto the exemplary embodiment of the present invention.

FIG. 5 is a perspective view illustrating a press unit in the electrodeassembly manufacturing apparatus according to the exemplary embodimentof the present invention.

FIG. 6 is a perspective view illustrating an example of a state in whichthe press unit presses a stack in the electrode assembly manufacturingapparatus according to the exemplary embodiment of the presentinvention.

FIG. 7 is a perspective view illustrating the stack table in theelectrode assembly manufacturing apparatus according to the exemplaryembodiment of the present invention.

FIG. 8 is a perspective view illustrating a first electrode seatingtable in the electrode assembly manufacturing apparatus according to theexemplary embodiment of the present invention.

FIG. 9 is a perspective view illustrating a second electrode seatingtable in the electrode assembly manufacturing apparatus according to theexemplary embodiment of the present invention.

FIG. 10 is a perspective view illustrating a first suction head in theelectrode assembly manufacturing apparatus according to the exemplaryembodiment of the present invention.

FIG. 11 is a bottom view illustrating the first suction head of FIG. 10, according to the exemplary embodiment of the present invention.

FIG. 12 is a top plan view illustrating the holding mechanism and thestack table in the electrode assembly manufacturing apparatus accordingto the exemplary embodiment of the present invention.

FIG. 13 is a front elevation view conceptually illustrating an electrodeassembly manufacturing apparatus according to another exemplaryembodiment of the present invention.

FIG. 14 is a perspective view of a separator heating unit of a separatorsupply unit according to the exemplary embodiment of the presentinvention.

FIG. 15A is a perspective view illustrating a first press unit accordingto the exemplary embodiment of the present invention, and FIG. 15B is aperspective view illustrating a second press unit according to theexemplary embodiment of the present invention.

DETAILED DESCRIPTION

The objects, specific advantages, and novel features of the presentinvention will become more apparent from the following detaileddescription taken in conjunction with the accompanying drawings andexemplary embodiments. In the present specification, in adding referencenumbers to the constituent elements of each drawing, it should be notedthat the same constituent elements are given the same number even thoughthey are indicated on different drawings. In addition, the presentinvention may be implemented in several different forms and is notlimited to the exemplary embodiments described herein. Further, indescribing the present invention, detailed descriptions of related knowntechnologies that may unnecessarily obscure the gist of the presentinvention will be omitted.

An exemplary embodiment of the present invention provides an electrodeassembly manufacturing method. The method may include: supplying a firstelectrode to a stack table; supplying a second electrode to the stacktable; supplying a separator to the stack table; and assembling a stackon the stack table by alternately stacking the first electrode and thesecond electrode on the separator, where the separator is sequentiallyfolded over a previously-stacked one of the first and second electrodesbefore a subsequent one of the first and second electrodes is stacked.After assembling the stack, the method may include performing a primaryheat press operation comprising gripping the stack with a gripper andthen heating and pressing the stack. After performing the primary heatpress operation, the method may further include removing the gripper andthen performing pre-heating on the stack, which includes heating andpressing the stack for 10 seconds to 40 seconds under a pressurecondition from 0.5 MPa to 2 MPa and a temperature condition from 50° C.to 85° C. After performing pre-heating on the stack, a secondary heatpress operation of heating and pressing the pre-heated stack may beperformed.

In the present invention, “pre-heating” refers to a process of heatingthe stack for a specific time with a constant pressure between theprimary heat press operation and the secondary heat press operation.

In the present invention, the “primary heat press” may be defined as anoperation of heating and pressing the stack before the operation ofpre-heating the stack.

In the present invention, the “secondary heat press” may be defined asan operation of heating and pressing the pre-heated stack.

In the present specification, FIG. 1 is a diagram schematicallyillustrating a method of manufacturing an electrode assembly accordingto an exemplary embodiment of the present invention. That is, referringto FIG. 1 , the method may first include a stack process of assembling astack (stack cell) on a stack table by alternately stacking the firstelectrode and the second electrode on the separator, where the separatoris sequentially folded over a previously-stacked one of the first andsecond electrodes before a subsequent one of the first and secondelectrodes is stacked. After the stack process, the stack may be movedaway from the stack table. During such time, the separator is pulled,and, after the separator is pulled for a predetermined length, theseparator is cut. Thereafter, the predetermined length of the cut end ofthe separator is wound around the stack cell. The movement of the stackaway from the stack table may be accomplished by the gripper, which isdesirably a moveable component that can grip the stack on the stacktable and then move the stack to the press unit, where the heat pressoperations are performed. The primary heat press operation is thenperformed in a state in which the wound stack cell is gripped with thegripper. After the primary heat press operation is completed, the gripof the stack cell by the gripper is released, and then the pre-heatingoperation is performed. After the pre-heating is completed, thesecondary heat press operation is performed. When the secondary heatpress operation is completed, the finished electrode assembly may becomplete.

According to an exemplary embodiment of the present invention, theprimary heat press operation may include: heating the stack table and/ora pair of pressing blocks; and pressing the stack between the pair ofheated pressing blocks, or between a pressing block and the stack table(either or both of which may be heated). The primary heat pressoperation may further include fixing the stack by pressing an uppersurface of the stack with the gripper. Such step of fixing the stack mayoccur prior to or concurrently with the step of heating the stack tableand/or the pair of pressing blocks.

According to an exemplary embodiment of the present invention, theprimary heat press operation may include heating and pressing the stackfor a time period from 5 seconds to 20 seconds under a temperaturecondition from 45° C. to 75° C. and under a pressure condition from 1Mpa to 2.5 Mpa. Preferably, the primary heat press operation may includeheating and pressing the stack for a time period from 10 seconds to 20seconds under a temperature condition from 45° C. to 65° C. and under apressure condition from 1 Mpa to 2 Mpa. More preferably, the primaryheat press operation may include heating and pressing the stack for atime period from 10 seconds to 20 seconds under a temperature conditionfrom 45° C. to 60° C. and under a pressure condition from 1 Mpa to 1.5Mpa.

According to an exemplary embodiment of the present invention, thesecondary heat press operation may include: ceasing the heating of thestack table and/or the pair of pressing blocks; ceasing the pressing ofthe stack; moving the gripper away from the stack; heating the stacktable and/or the pair of pressing blocks to transfer heat to the stack;and pressing the stack between the pair of pressing blocks, or pressingthe stack between a pressing block and the stack table (either or bothof which may be heated).

According to an exemplary embodiment of the present invention, thetemperature condition of the secondary heat press operation may be 50°C. or more, preferably 55° C. or more.

According to an exemplary embodiment of the present invention, thetemperature condition of the secondary heat press operation may be 85°C. or less.

According to an exemplary embodiment of the present invention, thetemperature condition of the secondary heat press operation may be from50° C. to 85° C., preferably from 55° C. to 85° C.

According to an exemplary embodiment of the present invention, thepressure condition of the secondary heat press operation may be 1 Mpa orless, and preferably 1.5 Mpa or less.

According to an exemplary embodiment of the present invention, thepressure condition of the secondary heat press operation may be 2.5 Mpaor less, and preferably 2 Mpa or less.

According to an exemplary embodiment of the present invention, thepressure condition of the secondary heat press operation may be from 1Mpa to 2.5 Mpa, preferably from 1.5 Mpa to 2.5 Mpa, and more preferablyfrom 1.5 Mpa to 2 Mpa.

According to an exemplary embodiment of the present invention, theheating and pressing of the secondary heat press operation may beperformed for 5 seconds or more.

According to an exemplary embodiment of the present invention, theheating and pressing of the secondary heat press operation may beperformed for 10 seconds or less, preferably 9 seconds or less, morepreferably 8 seconds or less.

According to an exemplary embodiment of the present invention, theheating and pressing of the secondary heat press operation may beperformed from 5 seconds to 10 seconds, preferably from 5 seconds to 9seconds, more preferably from 5 seconds to 8 seconds.

According to an exemplary embodiment of the present invention, thesecondary heat press operation may involve an operation of heating andpressing the stack for 5 seconds to 10 seconds under a temperaturecondition of 50° C. to 85° C. and a pressure condition of 1 Mpa to 2.5Mpa, preferably, for 5 seconds to 10 seconds under a temperaturecondition of 55° C. to 85° C. and a pressure condition of 1.5 Mpa ormore and 2.5 Mpa or less. More preferably, the secondary heat pressoperation may involve an operation of heating and pressing the stack for5 seconds to 10 seconds under a temperature condition from 50° C. to 85°C. and a pressure condition from 1.5 Mpa to 2 Mpa.

According to an exemplary embodiment of the present invention, thepre-heating may be performed between the primary heat press operationand the secondary heat press operation.

According to an exemplary embodiment of the present invention, apressure applied in the operation of pre-heating the stack may be lowerthan pressures applied in the primary heat press operation and thesecond press operation.

According to an exemplary embodiment of the present invention, thepre-heating may include: heating the pair of pressing blocks; andpressing the stack with the pair of pressing blocks.

According to an exemplary embodiment of the present invention, theprimary heat press operation, the pre-heating operation, and thesecondary heat press operation may utilize the same or different pairsof pressing blocks, and the pair of pressing blocks may each furtherinclude a press heater for heating the pair of pressing blocks.Moreover, according to exemplary embodiments of the invention, the stacktable may also include a stack table heater for heating the body of thestack table so as to transfer heat to the stack.

According to an exemplary embodiment of the present invention, the samepair of pressing blocks may be used in the primary heat press operation,the pre-heating operation, and the secondary heat press operation.

According to alternative embodiments, one or more of the heat pressoperations (i.e., the primary heat press operation, the pre-heatingoperation, and the secondary heat press operation) may occur on thestack table. In such cases, only one of the pressing blocks may beemployed to press the top of the stack down against the stack table. Inthat case, the gripper may be a holding mechanism of the stack table,which may stabilize the stack by securing the position of the stack withrespect to the stack table. Moreover, the holding mechanism may beconfigured to secure the stack in that manner at least during theprimary heat press operation.

According to an exemplary embodiment of the present invention, thepressure condition of the pre-heating operation may be 2.5 Mpa or less,and preferably 1.5 Mpa or less.

According to an exemplary embodiment of the present invention, thepressure condition of the pre-heating operation may be from 0.5 MPa to 2MPa, preferably from 0.5 MPa to 1.5 MPa.

According to an exemplary embodiment of the present invention, thetemperature condition of the pre-heating operation may be from 50° C. to85° C., preferably from 55° C. to 85° C.

According to an exemplary embodiment of the present invention, thepre-heating may involve heating and pressing the stack for 10 seconds ormore.

According to an exemplary embodiment of the present invention, thepre-heating may involve heating and pressing the stack for 40 seconds orless, more preferably 35 seconds or less.

According to an exemplary embodiment of the present invention, thepre-heating may involve heating and pressing the stack for a time periodfrom 10 seconds to 40 seconds, preferably from 10 seconds to 35 seconds.

According to an exemplary embodiment of the present invention, thepre-heating operation may be an operation of heating and pressing thestack for a time period from 10 seconds to 40 seconds under a pressurecondition from 0.5 MPa to 2 MPa and a temperature condition from 50° C.to 85° C., preferably, for a time period from 10 seconds to 35 secondsunder a pressure condition from 0.5 MPa to 1.5 MPa and a temperaturecondition from 55° C. to 85° C.

Herein, the pressure condition means the pressure applied by the pair ofpressing blocks (or by a pressure block against the stack table), andthe temperature condition means the temperature of heat applied by thebody of the stack table or the pair of pressing blocks.

In alternative embodiments, in which at least one of the heat pressoperations occurs on the stack table, as discussed above, the primaryheat press operation may involve one pressing block applying pressure tothe stack seated on the stack table, where the stack is heated by eitheror both of heaters in the stack table and/or the pressing block. Duringsuch primary heat press operation, the stack may be secured to the stacktable by a gripper in the form of a holding mechanism of the stacktable. After the primary heat press operation, the gripper may bereleased from the stack, and then a pre-heating operation andsubsequently a secondary heat press operation can be performed with thegripper disengaged from the stack. Such pre-heating and secondary heatpress operations may be performed on the stack table with pressureapplied by the same or a different pressing block. Or, the stack may bemoved to one or more separate press units, where the pre-heating andsecondary heat press operation may be performed by applying heat andpressure to the stack by one or more pairs of press blocks of the pressunit(s).

When the temperature, pressure, and time conditions disclosed herein arenot satisfied, the components of the electrode assembly may not beproperly adhered together, which can result in the electrode assemblyfalling apart or the components of the electrode assembly shifting theirpositions within the assembly, particularly when the electrode assemblyis moved before being inserted into a battery case. A problem may alsooccur in which the air permeability of the separator is excessivelyhigh.

On the other hand, when the heat press operations disclosed herein areperformed (including satisfying the respective pressure, temperature,and time conditions), an electrode assembly may be manufactured withoutthe need to individually heat and/or press each level of the electrodeassembly (i.e., heating and/or pressing each electrode and separatorpair at each step of the process) in order to bond the componentstogether. Such individual heat pressing at each level can detrimentallycause the effects of the heat and/or pressure to accumulate in the lowerseparators in the stack, since the already-stacked layers willexperience the heat and/or pressure of each application. That cannegatively impact such portions of separator by, for example, reducingporosity (and air permeability). In contrast, the present inventionallows the entire electrode assembly to be simultaneously bonded, whichimproves uniformity, among other things. It is thus possible tosimultaneously achieve both an appropriate level of adhesive forcebetween the electrodes and also achieve a separator having anappropriate amount of air permeability, all while minimizing damage tothe unit electrode.

According to the exemplary embodiment of the present invention, theoperation of manufacturing the stack by stacking the first electrode,the separator, and the second electrode on the stack table includes:stacking the separator on the stack table (S1); stacking the firstelectrode on the upper surface of the separator (S2); supplying theseparator while rotating the stack table to cover an upper surface ofthe first electrode (S3); and stacking the second electrode on a portionof the separator covering the upper surface of the first electrode (S4);and the operations of S1 to S4 may be repeated one or more times. Byrepeating the foregoing operations one or more times, zig zag folding ispossible in such a way that the separator becomes positioned betweeneach of the first and second electrodes.

According to the exemplary embodiment of the present invention, thestack comprising the separator and at least one each of the first andsecond electrodes may be held with the holding mechanism and therebyfixed to the stack table. The holding mechanism may also be referred toas a gripper.

According to the exemplary embodiment of the present invention, themethod may further include holding the first electrode or the secondelectrode by using the holding mechanism and fixing the first electrodeor the second electrode to the stack table when the first electrode orthe second electrode is stacked on the stack table. By doing this, it ispossible to prevent the position of the electrodes from shifting in theelectrode assembly.

The holding mechanism is used to prevent the stack of electrodes and theseparators from being distorted in the process for manufacturing theelectrode assembly. More particularly, the holding mechanism may pressand fix the upper surface of the stack (i.e., the upper surface of thefirst or second electrode or the separator stacked on the uppermost sideof the stack) when stacked on the stack table.

According to the exemplary embodiment of the present invention, theoperation of supplying the separator to the stack table may includecontinuously supplying (by unwinding) the separator while the separatorpasses through a passage of the separator supply unit.

According to the exemplary embodiment of the present invention, themethod may further include inspecting a stacking quality of the firstelectrode or the second electrode using image information obtainedthrough camera photography before stacking the first electrode or thesecond electrode.

According to the exemplary embodiment of the present invention, it ispossible to provide an electrode assembly manufactured by theabove-described manufacturing method. The electrode assembly has uniformadhesive force and air permeability across all layers of the assembly,and the thickness of each electrode is uniform. That is, any deviationin adhesive force, air permeability, and thickness of the electrodes isminimized across the electrode assembly.

In the present invention, a method for measuring adhesive force of theseparator is not particularly limited. In the method utilized anddiscussed further herein, a lower portion, a middle portion, and anupper portion of the electrode assembly were separated along thestacking direction of the electrode assembly, and samples were made ofeach of a positive electrode tab part, a middle part, and a negativeelectrode tab part in the width direction of the electrode assembly. Thesamples had a width of 55 mm and a length of 20 mm, and each sample mayinclude a positive electrode and a separator or a negative electrode anda separator. The sample was adhered to a slide glass, with the electrodebeing positioned on the adhesive surface of the slide glass.

More specifically, the slide glass with the sample adhered thereto wasmounted to an adhesive force measuring device, and values for force persample width (in grams/mm) were measured when the separator was peeledaway from the electrode according to the standard testing method setforth in ASTM-D6862. Specifically, an edge of the separator was pulledupwardly at 90° relative to the slide glass at a speed of 100 mm/min soas to peel the separator away from the electrode along the widthdirection of the sample (i.e., peeling from 0 mm to 55 mm).

In the present invention, the method for measuring the air permeabilityof the separator is not particularly limited. In the method utilized anddiscussed further herein, the air permeability was measured by using amethod commonly used in the art, namely, according to the JIS Gurleymeasurement method of the Japanese industrial standard using a Gurleytype Densometer (No. 158) manufactured by Toyoseiki. That is, the airpermeability of the separator was obtained by measuring the time ittakes for 100 ml (or 100 cc) of air to pass through the separator of 1square inch under a pressure of 0.05 MPa at room temperature.

FIG. 2 is a top plan view illustrating an example of the electrodeassembly manufacturing apparatus according to the exemplary embodimentof the present invention, and FIG. 3 is a front elevation viewconceptually illustrating the electrode assembly manufacturing apparatusaccording to the exemplary embodiment of the present invention. Here,for convenience, in FIG. 2 , the separator supply unit 120 illustratedin FIG. is omitted, and in FIG. 3 , the holding mechanism 170illustrated in FIG. 2 is omitted, and the press unit 180 located on therear side in a top plan view is illustrated with dotted lines.

Referring to FIGS. 2 and 3 , an apparatus 100 for manufacturing anelectrode assembly according to an exemplary embodiment of the presentinvention includes a stack table 110; a separator supply unit 120 forsupplying a separator 14; a first electrode supply unit 130 forsupplying a first electrode 11; a second electrode supply unit 140 forsupplying a second electrode 12; a first electrode stack unit 150 forstacking the first electrode 11 on the stack table 110; a secondelectrode stack unit 160 for stacking the second electrode 12 on thestack table 110; and a press unit 180 for bonding the first electrode11, the separator 14, and the second electrode 12 to each other. Thepress unit 180 may be used in all of the primary heat press operation,the pre-heating operation, and the secondary heat press operationdescribed above.

Further, the electrode assembly manufacturing apparatus 100 according tothe exemplary embodiment of the present invention may further include aholding mechanism 170 for fixing the first electrode 11 and the secondelectrode 12 to the stack table 110 when the first electrode 11 and thesecond electrode 12 are stacked on the stack table 110. In addition, theholding mechanism 170 may fix a stack of the first electrode(s) 11, theseparator 14, and the second electrode(s) 12.

Hereinafter, the electrode assembly manufacturing apparatus according tothe exemplary embodiment of the present invention will be described inmore detail with reference to FIGS. 2 to 12 .

FIG. 4 is a cross-sectional view illustrating an electrode assemblymanufactured by the electrode assembly manufacturing apparatus accordingto the exemplary embodiment of the present invention.

Referring to FIGS. 2 to 4 , the electrode assembly manufacturingapparatus 100 according to the exemplary embodiment of the presentinvention is an apparatus for manufacturing an electrode assembly 10 bystacking the first electrode 11, the separator 14, and the secondelectrode 12.

The electrode assembly 10 is a chargeable/dischargeable power generatingelement, and may be formed in a form in which the first electrode 11,the separator 14, and the second electrode 12 are alternately stackedand aggregated.

Here, in the electrode assembly 10, for example, the separator 14 may befolded in a zigzag shape, and the first electrode 11 and the secondelectrode 12 may be alternately disposed between the folded separators14. In this case, the electrode assembly 10 may be provided in a form inwhich the outermost portion is surrounded by the separator 14, e.g., bywrapping the separator around the assembled electrode assembly 10, asillustrated in FIG. 4 .

FIG. 5 is a perspective view illustrating the press unit in theelectrode assembly manufacturing apparatus according to the exemplaryembodiment of the present invention, and FIG. 6 is a perspective viewillustrating an example of a state in which the press unit presses astack in the electrode assembly manufacturing apparatus according to theexemplary embodiment of the present invention. More specifically, FIG. 6illustrates the above-described secondary heat press operation.

Referring to FIGS. 4 to 6 , the press unit 180 may press the firstelectrode(s) 11, separator 14, and second electrode(s) 12 which arestacked while being heated to bond the first electrode(s) 11, theseparator 14, and the second electrode(s) 12.

Further, the press unit 180 includes a pair of pressing blocks 181 and182, and the pair of pressing blocks 181 and 182 are moved towards oneanother to effect the pressing of the stack S comprising the stackedfirst electrode(s) 11, the separator 14, and the second electrode(s) 12.

In this case, when the separator 14 surrounds the outer surface of thestack S, the space between the outer portion of the separator 14positioned along the sides of the stack S and the portions of the firstand second electrodes 11 and 12 and the folded portions of the separator14 facing the outer portion may be bonded to one another. Accordingly,it is possible to more effectively prevent the positions of the firstand second electrodes 11 and 12 and the separator 14 from beingdisplaced and/or the components of the stack from separating from oneanother.

In addition, the press unit 180 further includes press heaters 183 and184 for heating the pair of pressing blocks 181 and 182, and the pair ofpressing blocks 181 and 182 may heat and press the stack S. Accordingly,when the stack S is pressed with the press unit 180, thermal fusionbetween the first electrode(s) 11, the separator 14, and the secondelectrode(s) 12 is better achieved, so that stronger adhesion may bepossible.

The pair of pressing blocks 181 and 182 has a flat pressing surface, andthe width and length dimensions of the pressing surface may be longerthan the confronting width and length dimensions of the stack S.

In addition, the pair of pressing blocks 181 and 182 includes a firstpressing block 181 and a second pressing block 182, and the firstpressing block 181 and the second pressing block 182 each define aquadrangular block having a rectangular parallelepiped form.

FIG. 7 is a perspective view illustrating the stack table in theelectrode assembly manufacturing apparatus according to the exemplaryembodiment of the present invention.

Referring to FIGS. 3 and 7 , the stack table 110 may include a tablebody 111 on which the first electrode 11, the separator 14, and thesecond electrode 12 are stacked, and a stack table heater 112 whichheats the table body 111 to transfer heat to the stacked stack S.

The first electrode 11 may be configured as a positive electrode, andthe second electrode 12 may be configured as a negative electrode, butthe present invention is not necessarily limited thereto. For example,the first electrode 11 may be configured as a negative electrode and thesecond electrode 12 may be configured as a positive electrode.

Referring to FIG. 3 , the separator supply unit 120 may supply theseparator 14 to the stack table 110. In particular, the separator supplyunit 120 may include a separator heating unit 121 defining the passagethrough which the separator 14 passes towards the stack table 110. Asshown in FIG. 14 , the separator heating unit 121 may include a pair ofbodies 121 a, each of which may be in the form of a square block, andthe bodies 121 a may be spaced apart by a distance defining one of thedimensions of the passage through which the separator 14 passes. Atleast one or both of the bodies 121 a may further include a separatorheater 121 b for heating the respective body 121 a, and therebytransferring heat to the separator 14.

The separator supply unit 120 may have a passage through which theseparator 14 passes towards the stack table 110. The separator supplyunit 120 may further include a separator roll 122 on which the separator14 is wound. Thus, the separator 14 wound on the separator roll 122 maybe gradually unwound and pass through the formed passage to be suppliedto the stack table 110.

FIG. 8 is a perspective view illustrating a first electrode seatingtable in the electrode assembly manufacturing apparatus according to theexemplary embodiment of the present invention.

Referring to FIGS. 3 and 8 , the first electrode supply unit 130 maysupply the first electrode 11 to the first electrode stack unit 150. Inaddition, the first electrode supply unit 130 may include a firstelectrode seating table 131 on which the first electrode 11 is seatedbefore being stacked on the stack table 110 by the first electrode stackunit 150.

The first electrode supply unit 130 may further include a firstelectrode roll 133 on which the first electrode 11 is wound in the formof a sheet, a first cutter 134 for cutting the first electrode 11 atregular intervals to form the first electrodes 11 of a predeterminedsize when the first electrode 11 is unwound and supplied from the firstelectrode roll 133, a first conveyor belt 135 for moving the firstelectrode 11 cut by the first cutter 134, and a first electrode supplyhead 136 for picking up (e.g., via vacuum suction) the first electrode11 transferred by the first conveyor belt 135 and seating the firstelectrode on the first electrode seating table 131. Here, the firstcutter 134 may cut the sheet-shaped first electrode 11 in such a way asto define a first electrode tab 11 a protruding from the end thereof.

FIG. 9 is a perspective view illustrating a second electrode seatingtable in the electrode assembly manufacturing apparatus according to theexemplary embodiment of the present invention.

Referring to FIGS. 3 and 9 , the second electrode supply unit 140 maysupply the second electrode 12 to the second electrode stack unit 160.In addition, the second electrode supply unit 140 may include a secondelectrode seating table 141 on which the second electrode 12 is seatedbefore being stacked on the stack table 110 by the second electrodestack unit 160.

The second electrode supply unit 140 may further include a secondelectrode roll 143 on which the second electrode 12 is wound in the formof a sheet, a second cutter 144 for cutting the second electrode 12 atregular intervals to form the second electrode 12 of a predeterminedsize when the second electrode 12 is unwound and supplied from thesecond electrode roll 143, a second conveyor belt 145 for moving thesecond electrode 121 cut by the second cutter 144, and a secondelectrode supply head 146 for picking up (e.g., via vacuum suction) thesecond electrode 12 transferred by the second conveyor belt 145 andseating the second electrode on the second electrode seating table 141.Here, the second cutter 144 may cut the sheet-shaped second electrode 12in such a way as to define a second electrode tab 12 a protruding fromthe end thereof.

FIG. 10 is a perspective view illustrating a first suction head in theelectrode assembly manufacturing apparatus according to the exemplaryembodiment of the present invention, and FIG. 11 is a bottom viewillustrating the first suction head in the electrode assemblymanufacturing apparatus according to the exemplary embodiment of thepresent invention.

Referring to FIGS. 3, 10, and 11 , the first electrode stack unit 150may stack the first electrode 11 on the stack table 110. The firstelectrode stack unit 150 may include a first suction head 151 and afirst moving unit 153. The first suction head 151 may pick up the firstelectrode 11 seated on the first electrode seating table 131 via vacuumsuction. In this case, the first suction head 151 may be formed with oneor more vacuum suction ports 151 a formed on a bottom surface 151 b ofthe first suction head 150 in order to apply suction to the firstelectrode 11 and thereby secure the first electrode 11 to the bottomsurface 151 b of the first suction head 151. In the first suction head151, a passage connecting the vacuum suction port 151 a and a device forgenerating vacuum suction (not illustrated) may be formed.

The first moving unit 153 may move the first suction head 151 to thestack table 110 so as to allow the first suction head 151 to stack thefirst electrode 11 on the stack table 110.

Meanwhile, referring to FIG. 3 , the second electrode stack unit 160 maystack the second electrode 12 on the stack table 110. The secondelectrode stack unit 160 may have the same structure as that of theforegoing first electrode stack unit 150. In such case, the secondelectrode stack unit 160 may include a second suction head 161 and asecond moving unit 163. The second suction head 161 may pick up thesecond electrode 12 seated on the second electrode seating table 141 viavacuum suction. The second moving unit 163 may then move the secondsuction head 161 to the stack table 110 so as to allow the secondsuction head 161 to stack the second electrode 12 on the stack table110.

FIG. 12 is a top plan view illustrating the holding mechanism and thestack table in the electrode assembly manufacturing apparatus accordingto the exemplary embodiment of the present invention.

Referring to FIGS. 2 and 12 , when the first electrode 11 or the secondelectrode 12 is stacked on the stack table 110, the holding mechanism170 may hold the first electrode 11 or the second electrode 12 andsecure the first electrode 11 or the second electrode 12 to the stacktable 110. In doing so, the holding mechanism 170 may apply pressure tothe upper surface of the stack S (i.e., the first electrode 11, thesecond electrode 12, or the separator 14 stacked on the uppermost end ofthe stack S). That is, when the first electrode(s) 11 and the secondelectrode(s) 12 are positioned in a stack S between layers of theseparator 14, the holding mechanism 170 may grip the uppermost surfaceof the stack by pressing the stack towards the stack table 110 toprevent movement of the stack S with respect to the stack table 110. Thegripper 170 may include, for example, a first holder 171 and a secondholder 172 to fix opposing sides of the first electrode 11 or the secondelectrode 12. The holders 171, 172 may each be in the form of one ormore clamps or other clamping mechanisms.

When the stack table 110 is rotated, while the holding mechanism 170maintains its hold on the first electrode 11 or the second electrode 12,the separator 14 may be supplied to the stack table 110 while beingunwound from the separator roll 122 in proportion to the rotation amountof the stack table 110. The holding mechanism 170 and the stack table110 may be connected or combined with the rotating device (notillustrated) that effects rotation of the stack table 110. Such rotatingdevice may include, for example, a mandrel or other form of rotating orpivoting shaft. Thus, when the holding mechanism 170 grips the firstelectrode 11 or the second electrode 12, the rotating device may rotatethe holding mechanism 170 with the stack table 110.

Hereinafter, the operation of the electrode assembly manufacturingapparatus 100 according to the exemplary embodiment of the presentinvention will be described.

Referring to FIGS. 2 to 4 , the separator 14 wound on the separator roll122 is supplied while passing through the passage formed so that theseparator can be stacked on the stack table 110.

Further, when the first electrode 11 is supplied from the firstelectrode supply unit 130 to the first electrode stack unit 150, thefirst electrode stack unit 150 stacks the first electrode 11 on theupper surface of the separator 14 stacked on the stack table 110.

The holding mechanism 170 then presses down on the upper surface of thefirst electrode 11 to secure the position of the first electrode 11 onthe stack table 110.

Thereafter, when the stack table 110 is rotated in the direction of thesecond electrode stack unit 160, the separator 14 is continuouslysupplied so as to cover the upper surface of the first electrode 11.

The second electrode 12 supplied from the second electrode supply unit140 is then stacked by the second electrode stack unit 160 on a portionof the separator 14 where the separator 14 covers the upper surface ofthe first electrode 11. Then the holding mechanism 170 releases theupper surface of the first electrode 11 and then presses down on theupper surface of the second electrode 12 to secure the position of thestack S being built vis-a-vis the stack table 110.

Thereafter, by repeating the process of stacking the first electrode 11and the second electrode 12, the stack S in which the separator 14 iszig-zag-folded and positioned between each of the successive first andsecond electrodes 11, 12 may be formed.

Then, the stack S is moved to the press unit 180, and the press unit 180heats and presses the stack S, thus thermally bonding the components ofthe stack together (i.e., the heated first electrode(s) 11, separator14, and second electrode(s) 12) so as to manufacture the electrodeassembly 10.

The stack S may be moved to the press unit by a gripper 51 that isconfigured to grip the stack on the stack table 110 and then move thestack to the press unit 180, where the heat press operations areperformed. Moreover, the press unit 180 may be divided into a firstpress unit 50 and a second press unit 60, where the first press unit 50can be used for the primary heat press operation (or pre-heating), andthe second press unit 60 can be used for the secondary heat pressoperation (or pre-heating).

Referring to FIGS. 15A and 15B, the first press unit 50 may primarilyheat and press the stack S in a fixed state. The first press unit 50includes a pair of first pressing blocks 50 a and 50 b and may furtherinclude the gripper 51 configured for fixing the stack S. In fixing thestack S, the gripper 51 may hold the stack S by pressing the upper andlower surfaces of the stack S towards one another along the stackingdirection (along the y axis) to fix the relative positions of the firstelectrodes 11, the second electrodes 12, and the separator 14. As in theexample shown, to hold these relative positions, the gripper 51 maypress the upper and lower surfaces of the stack S.

The pair of first pressing blocks 50 a and 50 b of the first press unit50 may move in directions towards and away from each other. In movingtowards each other, the pair of first pressing blocks 50 a and 50 b maycompress either one or both of the stack S and the gripper 51.

In this manner, the first press unit 50 may heat and compress the stackS to reduce or eliminate any spaces between the first electrodes 11, theseparator 14, and the second electrodes 12 included in the stack S, soas to bond such components of the stack S together.

As shown, each pressing surface of the pair of first pressing blocks 50a and 50 b configured for contact with and compression of the stack Smay define planes. At least one of the pair of first pressing blocks 50a and 50 b may include a gripper groove 52 having a shape correspondingto a fixing part 51 b of the gripper 51 described further herein. In theexample shown in FIG. 15A, each of the pair of first pressing blocks 50a and 50 b include four gripper grooves 52 to correspond with fourfixing parts 51 b. However, there may be a greater or fewer number ofgripper grooves 52. Preferably, the number of gripper grooves 52 shouldmatch the number of fixing parts to be used.

The gripper 51 may include a main body 51 a and a plurality of fixingparts 51 b. As in the arrangement shown, the main body 51 a may have alength along an x axis and a height along a y axis that are the same orapproximately the same as the length and height of the stack S alongthose respective axes. In some other arrangements, the main body may belonger than the length of the stack S in the x axis and have a greaterheight than the height of the stack S in the y axis. The fixing parts 51b preferably may be in the form of a rod, column, or plate that extendalong a width direction (z axis) of the stack S. Here, the length of thestack S in the x axis may refer to the portion of the stack having thelongest distance from one end to the other end of the stack S, and theheight in the y axis may refer to the distance in the stacking directionof the stack S, and the width in the z axis may refer to a distance in adirection perpendicular to both the x and y axes.

The fixing parts 51 b may be provided in two rows in which one row isadjacent to a pressing surface of pressing block 50 a while the otherrow is adjacent to a pressing surface of pressing block 50 b. Theposition of each of the fixing parts 51 b may be adjustable in theheight direction of the main body 51 a. In this manner, each of thefixing parts 51 b may be placed in contact with, and preferably alongthe width of, the upper and lower surfaces of the stack S to fix theposition of the stack S and the relative positions of the firstelectrode 11 and the second electrode 12 within the stack S.

In some arrangements, the second press unit 60 may heat and compress thestack S that was previously heated and compressed by the first pressunit 50, so as to secondarily compress the already primarily compressedstack S.

As shown in FIG. 15B, the second press unit 60 includes a pair of secondpressing blocks 60 a and 60 b. The pair of pressing blocks 60 a and 60 bmay be moved in directions towards and away from each other. In movingtowards each other, the pair of pressing blocks 60 a and 60 b may pressupon the upper and lower surfaces of the stack S to compress the stack.

As shown, each pressing surface of the pair of second pressing blocks 60a and 60 b configured for contact with and compression of the stack Smay define planes. As in the example shown, in some arrangements,grooves for the fixing parts 51 b may be excluded from the secondpressing blocks 60 a and 60 b. In some other arrangements, at least oneof the pair of second pressing blocks 60 a and 60 b may include one ormore grooves having a shape corresponding to the fixing part 51 b of thegripper 51.

In some arrangements, each of the pair of first pressing blocks 50 a and50 b of the first press unit 50 include gripper grooves 52 having ashape corresponding to the fixing part 51 b of the gripper 51, and eachof the pair of second pressing blocks 60 a and 60 b of the second pressunit 60 have flat pressing surfaces without any gripper grooves.

In some arrangements, the second press unit 60 may heat and press only aportion of the stack S on which the gripper 51 is (or was previously)located, which were not heated and pressed by the first press unit 50.In some other arrangements, the second press unit 50 may heat and pressthe entire upper and lower surfaces of the stack.

In some arrangements, the first press unit 50 may compress the heatedstack S initially and with the upper surface and the lower surface ofthe stack S fixed with the gripper 51 to reduce or eliminate the spacesbetween, while bonding, the first electrodes 11, the separator 14, andthe second electrodes 2 included in the stack S, so as to bond suchcomponents of the stack S together in the regions of the stack S inwhich the gripper 51 is not located.

In some such arrangements, the second press unit 60 may compress andheat the stack S which has already been preliminarily bonded by thefirst press unit 50, and from which the gripper 51 has been removed. Thesecond press unit 60 may thus reduce or eliminate any spaces between thefirst electrodes 11, the separator 4, and the second electrodes 12included in the stack S, so as to bond such components of the stack Stogether in the regions of the stack S in which the gripper 51previously pressed the stack S during the initial pressing operation bythe first press unit 50. In some such arrangements, each of the pair ofsecond pressing blocks 60 a and 60 b may be a quadrangular block in theform of a rectangular parallelepiped. In such arrangements, the pair ofsecond pressing blocks 60 a and 60 b may have the flat pressing surfacesdescribed previously herein.

In some arrangements, each of the pair of first pressing blocks 50 a and50 b of the first press unit may have the flat pressing surfaces. Insome such arrangements, each of the pair of second pressing blocks 60 aand 60 b of the second press unit 60 may have grooves having the shapecorresponding to the fixing parts 51 b of the gripper 51.

In some arrangements, the fixing part 51 b may include a heat-conductingmaterial, such as a thermally conductive metal material selected fromthe group consisting of aluminum and iron. By conducting heat to thestack S, when the first press unit 50 compresses the stack S fixed bythe gripper 51, the electrodes 11, 12, and separator 4 may be bondedtogether as the spaces between them are reduced or eliminated.

In some arrangements, the second press unit 60 may not compress regionsof the stack S on which the gripper 51 was previously located, but mayinstead only compress regions of the stack S where the gripper was notpreviously located and upon which the press unit 50 did not press duringthe initial pressing.

Further, each of the pair of first pressing blocks 50 a and 50 b may bea quadrangular block in the form of a rectangular parallelepiped. Insuch arrangements, the pair of first pressing blocks 50 a and 50 b mayhave the flat pressing surfaces described previously herein.

Either one or both of the first and second press units 50 and 60preferably include a press heater (not illustrated), configured forheating the respective pair of first and second pressing blocks 50 a, 50b, 60 a, and 60 b such that the blocks may heat the stack S whenpressing upon the stack. In this manner, when the stack S is pressedwith the first and second press units 50 and 60, thermal fusion betweenthe first electrodes 11, the separator 14, and the second electrodes 12may be better achieved such that stronger bond may be formed among theselayers.

In any one or more of the pairs of first and second pressing blocks 50a, 50 b, 60 a, and 60 b, both the length and the width of the respectivepressing surfaces may be greater than the corresponding length and width(in the x and z axes, respectively) of the stack S.

The electrode assembly manufacturing apparatus 100 according to theexemplary embodiment of the present invention configured as describedabove, by thermally bonding the components of the stack S to oneanother, may desirably prevent the stack S from falling apart or thecomponents of the stack S from shifting their positions within the stackS.

Hereinafter, an apparatus for manufacturing an electrode assemblyaccording to another embodiment of the present invention will bedescribed.

FIG. 13 is a front elevation view conceptually illustrating an electrodeassembly manufacturing apparatus according to another exemplaryembodiment of the present invention. In FIG. 13 , the holding mechanismis omitted for convenience, and the press unit 180 located on the rearside in a top plan view is illustrated with dotted lines.

Referring to FIG. 13 , an apparatus 200 for manufacturing an electrodeassembly according to another exemplary embodiment of the presentinvention includes a stack table 110; a separator supply unit 120 forsupplying a separator 14; a first electrode supply unit 130 forsupplying a first electrode 11; a second electrode supply unit 140 forsupplying a second electrode 12; a first electrode stack unit 150 forstacking the first electrode 11 on the stack table 110; a secondelectrode stack unit 160 for stacking the second electrode 12 on thestack table 110; a press unit 180 for bonding the first electrode 11,the separator 14, and the second electrode 12 to each other; and aholding mechanism 170 for securing the positions of the stack S on thestack table 110 (see FIG. 12 ).

The apparatus 200 according to this other embodiment may further includea rotating unit R for rotating the stack table 110 and a vision device290 for inspecting the first and second electrodes 11 and 12.

Accordingly, in the present exemplary embodiment, content overlappingwith the prior embodiment will be briefly described, while differencesfrom that prior embodiment will be primarily described.

In more detail, the vision device 290 of the apparatus 200 may include afirst camera 291 and a second camera 292. The first camera 291 mayphotograph the first electrode 11 seated on the first electrode seatingtable 131 in the first electrode supply unit 130, and the second camera292 may photograph the second electrode 12 seated on the secondelectrode seating table 141 in the second electrode supply unit 140. Thestacking quality of the first electrode 11 and the second electrode 12may thereby be inspected through image information obtained by the firstcamera 291 and the second camera 292. For example, the seatingpositions, sizes, and stacking states of the first electrode 11 and thesecond electrode 12 may thus be inspected.

The rotating unit R may rotate the stack table 110 in one direction r1and the other direction r2. A first electrode stack unit 150 may beprovided on one side of the rotating unit R, and the second electrodestack unit 160 may be provided on the other side of the rotating unit R.The rotating unit R may thus rotate the stack table 110 to one side soas to face a first suction head 151 when the first electrode 11 isstacked, and may rotate the stack table 110 to the other side so as toface a second suction head 161 when the second electrode 12 is stacked.By alternately rotating the stack table 110 between the orientationsfacing the first electrode stack unit 150 and the second electrode stackunit 160, the zig zag folding of the separator 14 between eachsuccessive one of the first and second electrodes 11, 12, as shown inFIG. 4 , may thus be achieved.

The apparatus 200 of the present embodiment and all of its subcomponentsoperates in the same manner as the apparatus 100 of thepreviously-described embodiment, except as otherwise stated. Forexample, when the first electrode 11 is supplied and seated on the firstelectrode seating table 131 of the first electrode supply unit 130, thestacking quality of the first electrode 11 may be inspected via thevision device 290. Similarly, when the second electrode 12 is suppliedand seated on the second electrode seating table 141 of the secondelectrode supply unit 140, the stacking quality of the second electrode12 may be inspected via the vision device 290.

In some arrangements of the present invention, the positive electrodemay be manufactured by, for example, coating a positive electrodecurrent collector with a positive electrode coating mixture comprising apositive electrode active material, a conductive material, and a binderand then drying the coating mixture. If necessary, a filler may be addedto the mixture. Such materials may be any appropriate materials used inthe relevant field, in particular those commonly used for the particularapplication.

For example, the positive electrode active material may include: layeredcompounds, such as lithium cobalt oxide (LiCoO₂) and lithium nickeloxide (LiNiO₂), or compounds substituted with one or more transitionmetals; lithium manganese oxides represented by the chemical formulaLi_(1+x)Mn_(2-x)O₄ (where x is 0 to 0.33), such as LiMnO₃, LiMn₂O₃, andLiMnO₂; lithium copper oxide (Li₂CuO₂); vanadium oxides, such as LiV₃O₈,LiFe₃O₄, V₂O₅, and Cu₂V₂O₇; Nickel (Ni) site-type lithium nickel oxiderepresented by the chemical formula LiNi_(1-x)M_(x)O₂ (wherein M=Co, Mn,Al, Cu, Fe, Mg, B or Ga, and x=0.01 to 0.3); lithium manganese compositeoxides represented by the chemical formula LiMn_(2-x)M_(x)O₂ (whereM=Co, Ni, Fe, Cr, Zn or Ta, and x=0.01 to 0.1) or Li₂Mn₃MO₈ (where M=Fe,Co, Ni, Cu, or Zn); LiMn₂O₄ in which a part of Li in the formula issubstituted with an alkaline earth metal ion; disulfide compounds; andFe₂(MoO₄)₃, but the positive electrode active material is not limited tosuch materials.

The materials that may be used for the positive electrode currentcollector is not particularly limited. The positive electrode currentcollector preferably has a relatively high conductivity without causinga chemical change when used in a battery. For example, stainless steel;aluminum; nickel; titanium; calcined carbon; or a material in which asurface of aluminum or stainless steel is treated with carbon, nickel,titanium, silver, and the like may be used. Preferably, the positiveelectrode current collector may be aluminum. Adhesion between thecurrent collector and the positive electrode coating mixture desirablymay be increased by including fine irregularities on a surface of thecurrent collector interfacing with the coating mixture. Moreover,various structural configurations of the positive electrode currentcollector may be used, such as a film, a sheet, a foil, a net, a porousbody, a foam body, and a non-woven body. The positive electrode currentcollector generally may have a thickness in a range from 3 μm to 500 μm.

The conductive material in the positive electrode coating mixturegenerally may be included in an amount from 1 to 50 wt % of the totalweight of the mixture including the positive electrode active material.The conductive material is not particularly limited and preferably hasconductivity without causing a chemical change when used in a battery.For example, graphite, such as natural graphite and artificial graphite;carbon black, such as carbon black, acetylene black, Ketjen black,channel black, furnace black, lamp black, and summer black; conductivefibers, such as carbon fibers and metal fibers; carbon and metalpowders, such as carbon fluoride, aluminum, and nickel powder;conductive whiskeys, such as zinc oxide and potassium titanate;conductive metal oxides, such as titanium oxide; and polyphenylenederivatives, may be used for the conductive material.

The binder in the positive electrode coating mixture assists in bondingbetween the active material and the conductive material in bonding thecoating mixture to the current collector. Such binder is generallyincluded in an amount from 1 to 50% by weight of the total weight of themixture including the positive electrode active material. Examples ofthe binder may include polyvinylidene fluoride, polyvinyl alcohol,carboxymethylcellulose (CMC), starch, hydroxypropylcellulose,regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene,polyethylene, polypropylene, ethylene-propylene-diene terpolymer (EPDM),sulfonated EPDM, styrene butylene rubber, fluororubber, and variouscopolymers.

The filler optionally added to the positive electrode coating mixturemay be used as a component to suppress the expansion of the positiveelectrode. Such a filler is not particularly limited and may include afibrous material that does not cause a chemical change when used in abattery. For example, olefin polymers, such as polyethylene and apolypropylene, and fibrous materials, such as glass fiber and carbonfiber, may be used.

In some arrangements, the negative electrode may be manufactured bycoating, drying, and pressing a negative electrode active material on anegative electrode current collector, and, if necessary, the conductivematerials, binders, fillers, and the like discussed above may beoptionally further included. In any event, any appropriate materialsused in the relevant field may be used, in particular those commonlyused for the particular application. For example, as the negativeelectrode active material, carbon, such as non-graphitizable carbon andgraphitic carbon; metal composite oxide represented by the chemicalformulas LixFe₂O₃(0≤x≤1), Li_(x)WO₂ (0≤x≤1), Sn_(x)Me_(1-x)Me′yOz (Me:Mn, Fe, Pb, Ge; Me′: Al, B, P, Si, elements of groups 1, 2 and 3 of theperiodic table, and halogens; 0<x≤1; 1≤y≤3; 1≤z≤8); lithium metal;lithium alloys; silicon-based alloys; tin-based alloys; metal oxides,such as SnO, SnO₂, PbO, PbO₂, Pb₂O₃, Pb₃O₄, Sb₂O₃, Sb₂O₄, Sb₂O₅, GeO,GeO₂, Bi₂O₃, Bi₂O₄, and Bi₂O₅; conductive polymers, such aspolyacetylene; and Li—Co—Ni-based materials may be used.

The materials that may be used for the negative electrode currentcollector are not particularly limited. The negative electrode currentcollector preferably has high conductivity without causing a chemicalchange in the battery. For example, copper; stainless steel; aluminum;nickel; titanium; calcined carbon; a material in which a surface ofcopper or stainless steel is surface-treated with carbon, nickel,titanium, silver, and the like; and an aluminum-cadmium alloy may beused. In addition, like the positive electrode current collector, thebond between the negative electrode current collector and the negativeelectrode active material may be strengthened by forming fineirregularities on the surface of the positive electrode currentcollector. Various structural configurations of the negative electrodecurrent collector may also be used, such as a film, a sheet, a foil, anet, a porous body, a foam body, a non-woven body, and the like. Inaddition, the negative electrode current collector may have a thicknessgenerally in a range of 3 μm to 500 μm.

In some arrangements, the separator may be an organic/inorganic complexporous SRS (Safety-Reinforcing Separator). The SRS may have a structurein which a coating layer component including inorganic particles and abinder polymer is coated on a polyolefin-based separator substrate.

Since the SRS does not undergo high-temperature thermal contraction dueto the heat resistance of the component inorganic particles, even if theelectrode assembly is penetrated by a needle-shaped conductor, anelongated length of the safety separator can be maintained.

The SRS may have a uniform porous structure formed by an interstitialvolume between the inorganic particles that are components of thecoating layer, in addition to the porous structure of the separatorsubstrate itself. The pores may not only significantly alleviate anyexternal impacts applied to the electrode assembly, but may alsofacilitate the movement of lithium ions through the pores, as well asenable a large amount of electrolyte to be impregnated into theseparator, thereby promoting improved performance of the battery.

In some arrangements, the separator may be dimensioned in its widthdimension (orthogonal to the longitudinal dimension in which theseparator is unrolled) such that separator portions extend outwardly onboth sides beyond corresponding edges of adjacent positive and negativeelectrodes (hereinafter “surplus portions”). Moreover, such outwardlyextending portions of the separator may have a structure including acoating layer thicker than a thickness of the separator formed on one orboth sides of the separator in order to prevent shrinkage of theseparator. For more information regarding the thicker coating layer onthe outwardly extending surplus portions of the separator, see KoreanPatent Application Publication No. 10-2016-0054219, the entire contentsof which are incorporated herein by reference. In some arrangements,each separator surplus portion may have a size of 5% to 12% of the widthof the separator. Moreover, in some arrangements, the coating layer maybe coated on both surfaces of the separator over a width of 50% to 90%of the width of each separator surplus portion. In addition, the widthsof the coating layers may be the same or different on each surface ofthe separator. In some arrangements, the coating layer may includeinorganic particles and a binder polymer as components.

In exemplary embodiments of the present invention, examples of thepolyolefin-based separator component may include high-densitypolyethylene, linear low-density polyethylene, low-density polyethylene,ultra-high molecular weight polyethylene, polypropylene, or derivativesthereof.

In some arrangements, the thickness of the coating layer may be smallerthan the thickness of the first electrode or the second electrode. Insome such arrangements, the thickness of the coating layer may be 30% to99% of the thickness of the first electrode or the second electrode.

In some arrangements, the coating layer may be formed by wet coating ordry coating.

In some arrangements, the polyolefin-based separator substrate and thecoating layer may exist in a form in which pores on the surface of thesubstrate and the coating layer are anchored with each other, wherebythe separator substrate and the coating layer may be bonded togetherfirmly.

The substrate and the coating layer of the separator may have athickness ratio from 9:1 to 1:9. A preferred thickness ratio may be 5:5.

In some arrangements, the inorganic particles may be inorganic particlescommonly used in the art. The inorganic particles may interact with eachother to form micropores in the form of empty spaces between theinorganic particles while structurally helping to maintain the physicalshape of the coating layer. In addition, since the inorganic particlesgenerally have properties that do not change their physical propertieseven at high temperatures of 200° C. or more, the resultantorganic/inorganic complex porous film generally and desirably hasexcellent heat resistance.

In addition, the materials that may be used for the inorganic particlesare not particularly limited but are preferably electrochemicallystable. That is, the inorganic particles are preferably selected suchthat oxidation and/or reduction reactions do not occur in the operatingvoltage range of the applied battery (for example, to 5 V based onLi/Li+). In particular, the use of inorganic particles having iontransport ability may improve performance by increasing the ionicconductivity in the electrochemical device. Thus, use of inorganicparticles having ionic conductivity as high as possible is preferable.In addition, when the inorganic particles have a high density, it isdifficult to disperse the inorganic particles during coating, and it canalso undesirably increase the weight of the battery. Therefore, use ofinorganic particles having density as low as possible is preferable. Inaddition, inorganic materials having a high dielectric constantcontribute to an increase in the degree of dissociation of electrolytesalt, such as a lithium salt, in a liquid electrolyte, thereby improvingthe ionic conductivity of the electrolyte.

For the above reasons, the inorganic particles may be at least one typeselected from the group consisting of inorganic particles havingpiezoelectricity and inorganic particles having lithium ion transportability.

Inorganic particles having piezoelectricity refer to materials which area nonconductor at normal pressure, but have a property of conductingelectricity due to a change in the internal structure when a certainpressure is applied. They are also materials which exhibit highpermittivity characteristics with a permittivity constant of 100 ormore. Inorganic particles having piezoelectricity also generate anelectric potential difference between opposing surfaces, e.g., of aseparator, by causing one surface to be positively charged and the othersurface to be negatively charged, or vice versa, when either tension orcompression is applied to an object composed of the inorganic particles,e.g., a separator.

When the inorganic particles having the above characteristics are usedas a coating layer component, in the case of an internal short circuitof both electrodes due to an external impact, such as by a needle-shapedconductor, the positive electrode and the negative electrode may notdirectly contact one another due to the inorganic particles coated onthe separator. Moreover, due to the piezoelectricity of the inorganicparticles, an electric potential difference may occur within theparticles, which desirably may result in electron movement between bothelectrodes (i.e., the flow of a minute current), so that it may bepossible to gently reduce the voltage of the battery, thereby improvingsafety.

Examples of materials for the inorganic particles havingpiezoelectricity may be one or more selected from the group consistingof BaTiO₃, Pb(Zr,Ti)O₃ (PZT), those represented by the chemical formulaPb_(1-x)La_(x)Zr_(1-y)Ti_(y)O₃ (PLZT), PB (Mg₃Nb_(2/3))O₃—PbTiO₃(PMN-PT), and hafnia (HfO₂), but are not limited to these materials.

Inorganic particles having lithium-ion transport ability refer toinorganic particles containing a lithium element but not storing lithiumand instead having a function of moving lithium ions. The inorganicparticles having lithium-ion transport ability are capable oftransporting and moving lithium ions due to a kind of defect in theparticle structure. As a result, the lithium-ion conductivity in thebattery may be improved, thereby improving battery performance.

Examples of materials for the inorganic particles having lithium-iontransport ability may be one or more selected from the group consistingof lithium phosphate (Li₃PO₄), lithium titanium phosphate (representedby the chemical formula Li_(x)Ti_(y)(PO₄)₃, wherein 0<x<2, 0<y<3),lithium aluminum titanium phosphate (represented by the chemical formulaLi_(x)Al_(y)Ti_(z)(PO₄)₃, wherein 0<x<2, 0<y<1, 0<z<3), glass of theseries represented by the chemical formula (LiAlTiP)_(x)O_(y) (0<x<4,0<y<13), lithium lanthanum titanate (represented by the chemical formulaLi_(x)La_(y)TiO₃, wherein 0<x<2, 0<y<3), lithium germanium thiophosphate(represented by the chemical formula Li_(x)Ge_(y)P_(z)S_(w), wherein0<x<4, 0<y<1, 0<z<1, 0<w<5), lithium nitride (represented by thechemical formula Li_(x)N_(y), wherein 0<x<4, 0<y<2), glass of the SiS₂series (represented by the chemical formula Li_(x)Si_(Y)S_(z), wherein0<x<3, 0<y<2, 0<z<4), and glass of the P₂S₅ series (represented by thechemical formula Li_(x)P_(Y)S_(z), wherein 0<x<3, 0<y<3, 0<z<7), but arenot limited to these materials.

The composition ratio of the inorganic particles and the binder polymer,which are components of the coating layer of the separator, is notparticularly limited, but may be adjusted within the range of 10:90 to99:1 by weight %, and preferably within the range of 80:20 to 99:1 byweight %. When the composition ratio is less than 10:90 by weight %, thecontent of the polymer may become excessively large and the pore sizeand porosity may be reduced due to a decrease in the empty space formedbetween the inorganic particles, finally resulting in deterioration ofthe battery performance. On the other hand, when the composition ratioexceeds 99:1 by weight %, the content of the polymer may be too small,and the mechanical properties of the final organic/inorganic compositeporous separator may become deteriorated due to weakened adhesive forcebetween the inorganic materials.

In some arrangements, a binder polymer commonly used in the art may beused as the binder polymer.

The coating layer of the organic/inorganic composite porous separatormay further include other commonly known additives in addition to theaforementioned inorganic particles and binder polymer.

In some arrangements, the coating layer may be referred to as an activelayer.

Although the present invention has been described in detail throughspecific exemplary embodiments, the present invention is not limitedthereto. Various different implementations may be made by those ofordinary skill in the art within the technical spirit of the presentinvention.

1) Example 1

19 positive electrode sheets, 20 negative electrode sheets, and anelongated separator were supplied to the stack table from the respectivepositive electrode supply unit, negative electrode supply unit, andseparator supply unit.

More specifically, the positive electrode and the negative electrodewere supplied after being cut from a positive electrode sheet and anegative electrode sheet, respectively, and the separator was suppliedin the form of an elongated separator sheet. Thereafter, the suppliedseparator was folded while rotating the stack table and stacking thepositive electrodes and the negative electrode as described above. Agripper was used to press down on and stabilize the stack, whichresulted in a stack including 39 electrodes.

After manufacturing the stack, a primary heat press operation wasperformed in a press unit by gripping the stack with the gripper andpressing for 15 seconds while heating the stack under a temperaturecondition of 50° C. and a pressure condition of 1.46 MPa.

After the primary heat press operation, a pre-heating operation wasperformed, in which the gripper was disengaged from the stack, thetemperature of the pressing blocks of the press unit were maintained at60° C. (temperature condition), and a pressure of 1 MPa (pressurecondition) was applied to the stack with the pressing blocks of thepress unit for 15 seconds (press time).

After the pre-heating operation, the secondary heat press operation wasperformed, in which the temperature of the pressing blocks weremaintained at 60° C. (temperature condition) and a pressure of 1.8 MPa(pressure condition) was applied to the stack with the pressing blocksfor 7 seconds (press time).

2) Examples 2 to 5 and Comparative Examples 1 to 17

Electrode assemblies of Examples 2 to 5 were manufactured in the samemethod as the electrode assembly manufacturing method in Example 1,except that the method was performed under the temperature conditions,pressure conditions, and press time represented in Table 1 below.

Electrode assemblies of Comparative Examples 1 to 17 were manufacturedby performing the primary and secondary heat press operations in thesame method as the electrode assembly manufacturing method of Example 1,except that the method was performed under the temperature conditions,pressure conditions, and press time represented in Tables 2 and 3 below.That is, in the case of Comparative Examples 1 to 12, the pre-heatingoperation was not performed.

TABLE 1 Primary heat press Pre-heating Secondary heat press TemperaturePressure Press Temperature Pressure Press Temperature Pressure Presscondition condition time condition condition time condition conditiontime (° C.) (MPa) (s) (° C.) (MPa) (s) (° C.) (MPa) (s) Example 1 501.46 15 60 1 15 60 1.8 7 Example 2 35 Example 3 70 15 70 Example 4 35Example 5 80 35 80

TABLE 2 Primary heat press Pre-heating Secondary heat press TemperaturePressure Press Temperature Pressure Press Temperature Pressure Presscondition condition time condition condition time condition conditiontime (° C.) (MPa) (s) (° C.) (MPa) (s) (° C.) (MPa) (s) ComparativeExample 1 50 1.46 15 — — — 60 1.8 25 Comparative Example 2 — — — 42Comparative Example 3 — — — 3 25 Comparative Example 4 — — — 42Comparative Example 5 — — — 70 1.8 25 Comparative Example 6 — — — 42Comparative Example 7 — — — 3 25 Comparative Example 8 — — — 42Comparative Example 9 — — — 80 1.8 25 Comparative Example 10 — — — 42Comparative Example 11 — — — 3 25 Comparative Example 12 — — — 42

TABLE 3 Primary heat press Pre-heating Secondary heat press TemperaturePressure Press Temperature Pressure Press Temperature Pressure Presscondition condition time condition condition time condition conditiontime (° C.) (MPa) (s) (° C.) (MPa) (s) (° C.) (MPa) (s) ComparativeExample 13 70 1 15 70 3 7 Comparative Example 14 35 Comparative Example15 80 1 15 80 3 7 Comparative Example 16 Comparative Example 17 90 4 4590 3 7

3) Experimental Example 1—Withstand Voltage Evaluation

Withstand voltages of the electrode assembles of Examples 1 to 5, andthe electrode assemblies of Comparative Examples 1 to 12 were measured.In particular, the voltage applied to the electrode assemblies ofExamples 1 to 5 and Comparative Examples 1 to 12 was increased from 0 Vto 4000 V, and the voltage value at the point in time when the leakagecurrent became 0.6 mA or more was measured and determined to be thewithstand voltage values.

The results are represented in Table 4 below.

TABLE 4 Pressure condition of Total Withstand secondary press voltageheat press time (kV) (MPa) (s) Example 1 1.72 1.8 37 Example 2 1.53 1.857 Example 3 1.57 1.8 37 Example 4 1.57 1.8 57 Example 5 1.66 1.8 57Comparative Example 1 1.67 1.8 40 Comparative Example 2 1.42 1.8 57Comparative Example 3 1.52 3.0 40 Comparative Example 4 1.35 3.0 57Comparative Example 5 1.4 1.8 40 Comparative Example 6 1.33 1.8 57Comparative Example 7 1.52 3.0 40 Comparative Example 8 1.28 3.0 57Comparative Example 9 1.8 1.8 40 Comparative Example 10 1.13 1.8 57Comparative Example 11 1.37 3.0 40 Comparative Example 12 1.25 3.0 57

In general, the main factor that causes damage to the electrode assemblyis a pressure condition.

From the results of Table 4, comparing Comparative Examples 1 to 12 (inwhich the pre-heating operation was omitted) to Examples 1 to 5 (usingthe electrode assembly manufacturing method of the present invention),it was confirmed that even if the pressure conditions of the secondaryheat press operation were the same and the total time (total press time)for heating and pressing in the entire process was the same, theelectrode assembly manufacturing method according to the presentinvention nevertheless resulted in the electrode assembly having betterwithstand voltage.

In addition, it was confirmed from Examples 1 and 3 that it was possibleto manufacture an electrode assembly having excellent withstand voltagewhile reducing the total time (total press time) of heating and pressingin the entire process. Thus, such examples result in efficiencyimprovement and cost reduction of the entire process.

4) Experimental Example 1—Evaluation of Adhesive Force

Adhesive forces between surfaces at the upper end, the lower end, andthe middle of the stack S were measured by disassembling (i.e.,separating the layers of) the electrode assemblies of Examples 1 to 6and Comparative Examples 4, 8, and 11 to 17 (in which the separation ofthe electrodes and separator were not observed before 60 seconds in theprevious test) and then analyzing the separated layers. Specifically,adhesive force between the negative electrode and the separator locatedat the lowermost end of the stack was measured. Additionally, adhesiveforce between the negative electrode and the separator located at theuppermost end of the stack was measured. Finally, adhesive force betweenthe negative electrode and the separator located at a middle locationalong the stacking direction of the stack was measured

In each of the separated electrode assemblies, the negative electrodeand the separator sampled had a width of 55 mm and a length of 20 mm.The sampled sample was adhered to the slide glass with the electrodebeing positioned on the adhesive surface of the slide glass. After that,the slide glass with the sample was mounted to the adhesive forcemeasuring device and tested by performing 90° peel test at a speed of100 mm/min pursuant to the testing method set forth in ASTM-D6862, asdiscussed above. After discounting any initial significant fluctuations,the values for applied force per sample width (in grams/mm) weremeasured while the separator was peeled away from the electrode.

The results are represented in Table 5 below.

TABLE 5 Negative electrode adhesive force (gf/20 mm) Upper Lower surfaceMiddle surface Deviation Example 1 10.2 3.8 19 10.8 Example 2 11 5.917.1 8.15 Example 3 14.3 5.7 8.4 5.65 Example 4 15.1 8.1 16.2 7.55Example 5 21.1 8.2 23.4 14.05 Comparative 37.7 18.4 40.9 20.9 Example 4Comparative 55 34.7 56.3 20.95 Example 8 Comparative 63.4 18.9 54 39.8Example 11 Comparative 65.9 39.4 73.3 30.2 Example 12 Comparative 24.48.7 26.1 16.55 Example 13 Comparative 33.6 14.3 33.8 19.4 Example 14Comparative 28.7 12.9 40.1 21.5 Example 15 Comparative 49.2 18.4 45.528.95 Example 16 Comparative 104.8 90.3 100.5 12.35 Example 17

From the results of Table 5, in Comparative Examples 4, 8, 11, and 12,in which the secondary heat press operation was performed at 3 MPa(which is a pressure condition higher than 2.5 MPa), withoutpre-heating, it was confirmed that at least one of the adhesive forcevalues among the different positions of the electrode assembly exceeded35 gf/20 mm.

In addition, it was confirmed through Comparative Examples 12 to 17 thateven when pre-heating was performed, at least one of the adhesive forcevalues among the different positions of the electrode assembly exceeded35 gf/20 mm, even when the secondary heat press operation was performedat 3 MPa (which is a pressure condition higher than 2.5 MPa).

In particular, in the case of Comparative Examples 14 and 16, in whichthe pre-heating time exceeded 30 seconds while the pre-heating pressureand temperature conditions of the electrode assembly of the presentinvention were satisfied, and in the case of Comparative Example 17, inwhich the pre-heating was performed, but all of the pre-heatingpressure, temperature, and time conditions of the electrode assembly ofthe present invention were not satisfied, it was confirmed that at leastone of the adhesive force values among the different positions of theelectrode assembly greatly exceeded 35 gf/20 mm.

When the adhesive force of the electrode assembly exceeds 35 gf/20 mm,there are disadvantages in that cleaning and process handling are noteasy (so the cost of the process may increase), and air permeability ispoor (so that it is difficult to produce an electrode assembly havinguniform electrolyte wetting).

On the other hand, it was confirmed that when the electrode assembly wasmanufactured by the electrode assembly manufacturing method of thepresent invention, the cleaning and the process handling were easy, andthe electrode assembly had uniform performance.

In addition, in the case of Examples 1 to 4, since the deviation in theadhesive force was small, it was confirmed that such electrodeassemblies had more uniform performance.

What is claimed is:
 1. A method of manufacturing an electrode assembly,comprising: assembling an electrode stack including a plurality ofelectrodes stacked along a stacking axis with a respective separatorportion positioned between each of the electrodes; after assembling theelectrode stack, performing a primary heat press operation on theelectrode stack, the primary heat press operation comprising applyingheat and pressure to the electrode stack; after the primary heat pressoperation, performing a pre-heating operation on the electrode stack;and after the pre-heating operation, performing a secondary heat pressoperation on the electrode stack, the secondary heat press operationcomprising applying heat and pressure to the electrode stack, whereinthe pre-heating operation includes applying heat and pressure to theelectrode stack for a time period from 10 seconds to 40 seconds under apressure condition from 0.5 MPa to 2 MPa and under a temperaturecondition from 50° C. to 85° C., and wherein the pressure conditionapplied in the pre-heating operation includes applying a lower pressurethan that applied in the primary heat press operation and the secondaryheat press operation.
 2. The method of claim 1, wherein the primary heatpress operation includes engaging the electrode stack with a gripper tosecure a position of the electrode stack, and wherein applying heat andpressure to the electrode stack during the primary heat press operationoccurs while the gripper is engaged with the electrode stack.
 3. Themethod of claim 2, further comprising disengaging the gripper from theelectrode stack before performing the pre-heating operation.
 4. Themethod of claim 1, wherein the separator portions are portions of anelongated separator sheet, and wherein the step of assembling theelectrode stack includes alternately stacking a first one of theelectrodes and a second one of the electrodes on the elongated separatorsheet, where the elongated separator sheet is sequentially folded over apreviously-stacked one of the first and second electrodes before asubsequent one of the first and second electrode is stacked.
 5. Themethod of claim 4, wherein the step of assembling the electrode stackincludes: (1) positioning the elongate separator sheet on a stack table;(2) stacking one of the first electrodes on an upper surface of theelongated separator sheet; (3) rotating the stack table while coveringan upper surface of the one of the first electrodes with the elongatedseparator sheet; and (4) stacking one of the second electrodes on aportion of the elongated separator sheet covering the upper surface ofthe one of the first electrodes, wherein the above steps (1) to (4) arerepeated one or more times.
 6. The method of claim 4, further comprisingusing a camera to inspect the stacking of the first electrode or thesecond electrode.
 7. The method of claim 1, wherein the primary heatpress operation includes applying heat and pressure to the electrodestack for a time period from 5 seconds to 20 seconds under a temperaturecondition from 45° C. to 75° C. and under a pressure condition of 1 Mpato 2.5 Mpa.
 8. The method of claim 1, wherein the secondary heat pressoperation includes applying heat and pressure to the electrode stack fora time period from 5 seconds to 10 seconds under a temperature conditionfrom 50° C. to 85° C. and under a pressure condition of 1 Mpa to 2.5Mpa.
 9. The method of claim 1, wherein the steps of applying pressure tothe electrode stack in both of the primary and secondary heat pressoperations include advancing a pressing block along the stacking axisand into engagement with the electrode stack.
 10. The method of claim 9,wherein the pressing block is heated to transfer heat to the electrodestack.
 11. The method of claim 1, wherein the step of assembling theelectrode stack includes winding an elongated separator sheet around anouter circumference of the electrode stack.
 12. The method of claim 1,further comprising heating at least one of the electrodes and theseparator portions before the step of assembling the electrode stack.